List Core JS polyfills for browserslist environments (#16356)

build-scripts/list-plugins-and-polyfills.js

@@ -0,0 +1,59 @@
+#!/usr/bin/env node
+// Script to print Babel plugins and Core JS polyfills that will be used by browserslist environments
+
+import { version as babelVersion } from "@babel/core";
+import presetEnv from "@babel/preset-env";
+import compilationTargets from "@babel/helper-compilation-targets";
+import coreJSCompat from "core-js-compat";
+import { logPlugin } from "@babel/preset-env/lib/debug.js";
+import { babelOptions } from "./bundle.cjs";
+
+const detailsOpen = (heading) =>
+  `<details>\n<summary><h4>${heading}</h4></summary>\n`;
+const detailsClose = "</details>\n";
+
+const dummyAPI = {
+  version: babelVersion,
+  assertVersion: () => {},
+  caller: (callback) =>
+    callback({
+      name: "Dummy Bundler",
+      supportsStaticESM: true,
+      supportsDynamicImport: true,
+      supportsTopLevelAwait: true,
+      supportsExportNamespaceFrom: true,
+    }),
+  targets: () => ({}),
+};
+
+for (const buildType of ["Modern", "Legacy"]) {
+  const browserslistEnv = buildType.toLowerCase();
+  const babelOpts = babelOptions({ latestBuild: browserslistEnv === "modern" });
+  const presetEnvOpts = babelOpts.presets[0][1];
+
+  // Invoking preset-env in debug mode will log the included plugins
+  console.log(detailsOpen(`${buildType} Build Babel Plugins`));
+  presetEnv.default(dummyAPI, {
+    ...presetEnvOpts,
+    browserslistEnv,
+    debug: true,
+  });
+  console.log(detailsClose);
+
+  // Manually log the Core-JS polyfills using the same technique
+  if (presetEnvOpts.useBuiltIns) {
+    console.log(detailsOpen(`${buildType} Build Core-JS Polyfills`));
+    const targets = compilationTargets.default(babelOpts?.targets, {
+      browserslistEnv,
+    });
+    const polyfillList = coreJSCompat({ targets }).list;
+    console.log(
+      "The following %i polyfills may be injected by Babel:\n",
+      polyfillList.length
+    );
+    for (const polyfill of polyfillList) {
+      logPlugin(polyfill, targets, coreJSCompat.data);
+    }
+    console.log(detailsClose);
+  }
+}

build-scripts/list-preset-env-plugins.js

@@ -1,30 +0,0 @@
-#!/usr/bin/env node
-// Script to print Babel plugins that will be used by browserslist environments
-
-import { version as babelVersion } from "@babel/core";
-import presetEnv from "@babel/preset-env";
-import { babelOptions } from "./bundle.cjs";
-
-const dummyAPI = {
-  version: babelVersion,
-  assertVersion: () => {},
-  caller: (callback) =>
-    callback({
-      name: "Dummy Bundler",
-      supportsStaticESM: true,
-      supportsDynamicImport: true,
-      supportsTopLevelAwait: true,
-      supportsExportNamespaceFrom: true,
-    }),
-  targets: () => ({}),
-};
-
-for (const browserslistEnv of ["modern", "legacy"]) {
-  console.log("\nBrowsersList Environment = %s\n", browserslistEnv);
-  presetEnv.default(dummyAPI, {
-    ...babelOptions({ latestBuild: browserslistEnv === "modern" })
-      .presets[0][1],
-    browserslistEnv,
-    debug: true,
-  });
-}